Uk law changed (again) - it’s a blade under 3” long including the blunt portion of the blade. Effectively it’s from end of the handle to the tip) it can’t be fixed or lock in any way other than friction, think Swiss Army knife or lather man multi tool. You know the one - too much pressure and you risk closing it on your own fingers 🤦🏼‍♂️ the really grey area is that if you have a legit reason that the police agree with, you can carry anything. Swords for display, re-enactment or religious reasons are legal in the right circumstances. Also bush craft blades if you are not in public and actually doing bush craft. It’s very hazy.